Michael Ian Friswell

Michael Ian Friswell
Swansea University | SWAN · College of Engineering

MA, MSc, PhD, DSc

About

849
Publications
310,901
Reads
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26,981
Citations
Additional affiliations
January 2009 - present
Swansea University
Position
  • Professor of Aerospace Structures
September 2002 - December 2008
University of Bristol
Position
  • Sir George White Professor of Aerospace Engineering
September 1987 - July 1993
Aston University
Position
  • Lecturer

Publications

Publications (849)
Article
The complex dynamics of a frictional contact interface have been the subject of many research investigations. However, a comprehensive model has not been proposed that can be easily solved and considers the effect of all parameters of interest, i.e., the variation in contact pressure, the interaction of normal and tangential direction mechanisms, a...
Article
Vibration-based energy harvesting represents a clean power technology that can be of interest for application in civil engineering structures. This study focuses on energy harvesting using cantilever piezoelectric devices excited by operational and ambient bridge vibration. The optimal design and analysis of energy harvesters is usually performed u...
Article
Full-text available
A parameter study is presented to determine effects of planet gear design parameters on the global modal behaviour of planetary geared rotor systems. The modal sensitivity analysis is conducted using a three-dimensional dynamic model of a planetary geared rotor system for the number of planet gears, planet mistuning, mass of planet gears, gear mesh...
Article
Full-text available
This work develops a morphing concept that utilises a metamaterial as the passive morphing device for helicopter blades. The metamaterials are created with bend-twist coupling, which enable the blade twist under prescribed bending loads. Finite element analysis (FEA) is performed to investigate the influence of the unit cell configurations on the c...
Conference Paper
Full-text available
This work explores the closed-loop response of the MODFLEX flexible wing in the presence of 1-cosine gusts. The ultimate aim of the project is to investigate the effects of gusts on a structurally nonlinear system and to apply linear/nonlinear active control, aiming to mitigate the vibration of the system which would reduce the loads introduced int...
Article
A common issue with morphing structures is that the actuators must work against significant structural and aerodynamic stiffness. The concept of passive energy balancing (PEB) aims to ameliorate this, and thereby reduces system mass, by connecting negative stiffness elements to the actuated degrees of freedom. However, these devices can be complex...
Chapter
Despite all the efforts made to investigate the dynamics of jointed structures, they still remain as one of the uncertain dynamical systems in structural dynamics. Modelling the dynamic behaviour of bolted joint contact interfaces is one of the most challenging tasks in structural dynamics. The multi-frequency response of nonlinear systems, particu...
Chapter
In jointed structures, both stiffness and damping properties are affected by the way that the contact interfaces behave. The overall behaviour of the contact interface is the result of different parameters; among them are the contact surface quality and interface pressure distribution. Small changes in these parameters result in a considerable chan...
Article
The idea of morphing a helicopter blade by using compliant structures promises augmented capabilities in terms of manoeuvrability and fuel efficiency. To achieve morphing, compliant structures work by elastically deforming to achieve the desired response, and therefore actuation must work against the inherent structural stiffness in addition to ext...
Article
Full-text available
A vane-type gust generator has been designed and characterized in the Swansea University wind tunnel to enable the validation of the response of aircraft models to gust loads. The experimental results reveal the complexity of the flow between the gust vanes and the aircraft model location. Previous studies have shown that generating a predetermined...
Conference Paper
Full-text available
The development of lighter and more efficient transport aircraft has led to an increased focus on gust load alleviation. A recent consideration in aircraft design is using hinged wing tip devices to increase the aspect ratio, improving aircraft performance. Moreover, numerical studies have suggested using the wing tips during flight to provide addi...
Conference Paper
Full-text available
In this paper, the effect of a nonlinear energy sink (NES) device on the aeroelastic and gust response of an aircraft wing with a hardening stiffness structural nonlinearity is investigated. The structural dynamics of the wing is simulated using a 2-DOF typical section which undergoes pitch and heave (plunge) motions. Furthermore, the wing is subje...
Article
Full-text available
The present study performs a set of static tests to demonstrate a novel passive morphing concept. The concept introduces a bend-twist coupled composite spar to rotor blades, allowing for twist morphing to be achieved by imposing a lagwise bending moment using centrifugal forces produced by a movable mass at the blade tip. First, three composite spa...
Article
An understating on interaction between a rotating flexible member and a stationary element has a wide range of industrial applications. The focus of this study was to understand the modal interactions using a conceptual model. The conceptual model of the system consists of multiple disc rotors with a localised conduit. A theoretical model of the sy...
Conference Paper
A vane type gust generator has been designed and characterized in the Swansea University wind tunnel to enable the validation of the response of aircraft models to gust loads. The experimental results reveal the complexity of the flow between the gust vanes and the aircraft model location. Previous studies have shown that generating a predetermined...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-0172.vid A common issue with morphing structures is that the actuators must work against significant structural and aerodynamic stiffness. The concept of Passive Energy Balancing (PEB) aims to ameliorate this, and thereby reduce system mass, by connecting negative stiffness elements to the act...
Article
Full-text available
In recent years, the development of lighter and more efficient transport aircraft has led to an increased focus on gust load alleviation. A recent strategy is based on the use of folding wingtip devices that increase the aspect ratio and therefore improve the aircraft performance. Moreover, numerical studies have suggested such a folding wingtip so...
Article
Full-text available
Testing nonlinear structures to characterise their internal nonlinear forces is challenging. Often nonlinear structures are excited by harmonic forces and yield a multi-harmonic response. In many systems, particularly ones with strong nonlinearities, the effect of higher harmonics in the force and responses cannot be ignored. Even if the intended e...
Chapter
Parametric excitation is introduced to amplify the external harmonic excitation and extend the capabilities of a nonlinear piezoelectric energy harvester device. To investigate the efficiency of the parametrically amplified energy harvester, the time responses of the voltage and power are computed using the state space formulation. It is assumed th...
Chapter
Parametric excitation is introduced to amplify the external harmonic excitation and extend the capabilities of a nonlinear piezoelectric energy harvester device. To investigate the efficiency of the parametrically amplified energy harvester, the time responses of the voltage and power are computed using the state space formulation. It is assumed th...
Article
The dynamics of elastic cantilevered smart pipes conveying fluid with non-uniform flow velocity profiles is presented for optimal power generation. The Navier-Stokes equations are used to model the incompressible flow in the circular smart pipe, and flow profile modification factors are formulated based on the Reynolds number and Darcy friction fac...
Conference Paper
Full-text available
Analytically obtained bearing dynamic characteristics have been a major source of error in the modelling and analysis of large turbo-generators. An experimental estimation algorithm for bearing dynamic characterisation by using unbalance response measurements is presented for flexible rotor-bearing systems. The algorithm estimates the bearing dynam...
Article
Full-text available
This paper addresses the influence of manufacturing variability of a helicopter rotor blade on its aeroelastic responses. An aeroelastic analysis using finite elements in spatial and temporal domains is used to compute the helicopter rotor frequencies, vibratory hub loads, power required and stability in forward flight. The novelty of the work lies...
Conference Paper
Full-text available
A vane-type gust generator has been designed and characterised in the Swansea University wind tunnel to validate the response of aircraft models to gust loads. Experimental results reveal the complex dynamics of the airflow in the wake of the two gust generator vanes. More specifically, imposing '1-cos' vane rotation does not produce an exact '1-co...
Article
Full-text available
Rotating machines are intrinsically susceptible to expensive and high-risk faults such as rotor–stator rub. During a rub event normal and tangential forces are generated by the contact and friction that cause wear at the contacting interfaces. In the present work, such forces are computed by assuming linear elastic contact and Coulomb friction at m...
Preprint
Full-text available
With increasing demand for rotor blades in applications such as wind turbines, helicopters, and unmanned aircrafts , improving the performance of such structures using morphing blades has received considerable attention. Resonant passive energy balancing is a relatively new concept introduced to minimize the required actuation energy. This study in...
Article
Full-text available
We demonstrate that the consideration of material uncertainty can dramatically impact the optimal topological micro‑structural configuration of mechanical metamaterials. The robust optimization problem is formulated in such a way that it facilitates the emergence of extreme mechanical properties of metamaterials. The algorithm is based on the bi‑di...
Article
Periodic structures attenuate wave propagation in a specified frequency range, such that a desired bandgap behaviour can be obtained. Most periodic structures are produced by additive manufacturing. However, it is recently found that the variability in the manufacturing processes can lead to a significant deviation from the desired behaviour. This...
Article
Full-text available
Nonlinearities in rotating systems have been seen to cause a wide variety of rich phenomena; however, the understanding of these phenomena has been limited because numerical approaches typically rely on “brute force” time simulation, which is slow due to issues of step size and settling time, cannot locate unstable solution families, and may miss k...
Article
Full-text available
A novel passive twist morphing concept is examined for helicopter blades. The concept is demonstrated using a thin-walled rectangular composite beam created with symmetric layup to obtain bend-twist property. The twist of a rotor blade is proposed to be actuated though a movable mass at the blade tip which is able to provide a range of lagwise bend...
Article
This study develops a comprehensive vibrational analysis of rotating nanobeams on visco-elastic foundations with thermal effects based on the modified couple stress and Eringen’s nonlocal elasticity theories. This approach accurately simulates the nonlocal stress and size effects. Higher-order shear deformation beam theory and the generalized diffe...
Article
Full-text available
The dynamic response of individual components in an assembled structure shows high accuracy compared to experimental measurements of the system response. However, when it comes to assemblies, the conventional linear approaches fail to deliver good accuracy, due to the uncertain linear and nonlinear mechanisms in the contact interface of the joints....
Article
Bistable composite laminates are advanced composite structures which are potential candidates for morphing structure applications. The geometrical dimensions, material properties, ambient temperature and moisture have significant effects on the bistable behaviour, and the effect of uncertain parameters should be quantified. Reliability analysis is...
Article
Full-text available
Gust and turbulence events are of primary importance for the analysis of flight incidents, for the design of gust load alleviation systems and for the calculation of loads in the airframe. Gust and turbulence events cannot be measured directly but they can be obtained through direct or optimisation-based methods. In the direct method the discretisa...
Article
Full-text available
In this paper, the effect of distributed electric propulsion on the aeroelastic stability of an electric aircraft wing was investigated. All the electric propulsors, which are of different properties, are attached to the wing of the aircraft in different positions. The wing structural dynamics was modelled by using geometrically exact beam equation...
Article
Full-text available
A novel approach for mode shape feature extraction and model updating of axisymmetric structures based on radial Tchebichef moment (RTM) descriptors is proposed in this study. The mode shape features extracted by RTM descriptors can effectively compress the full-field modal vibration data and retain the most important information. The reconstructio...
Article
To reduce the computational cost of assembled stochastic linear structural dynamic systems, a three-staged reduced order model-based framework for forward uncertainty propagation was developed. First, the physical domain was decomposed by constructing an equivalent reduced order numerical model that limited the cost of a single deterministic simula...
Article
A rotor can contact a stator thereby inducing some very strong non-linearities that can result in a plethora of vibration phenomena. Synchronous motions, chaotic motion, backward whirl, forward whirl are some of the reported phenomena in the literature. This article presents an experimental approach based on a very flexible rotor rig designed with...
Article
This paper characterizes the stochastic dynamic response of periodic structures by accounting for manufacturing variabilities. Manufacturing variabilities are simulated through a probabilistic description of the structural material and geometric properties. The underlying uncertainty propagation problem has been efficiently carried out by functiona...
Article
The optimum position and minimum restraint stiffness of a flexible point support to raise a natural frequency of a thin bending plate is investigated, with the inclusion of the corresponding additional support mass. First the derivatives of the natural frequencies of the plate structure are derived with respect to the support movement using a finit...
Conference Paper
Parametric excitation is introduced to amplify the external harmonic excitation and extend the capabilities of a nonlinear piezoelectric energy harvester device. To investigate the efficiency of the parametrically amplified energy harvester, the time responses of the voltage and power are computed using the state space formulation. It is assumed th...
Article
In this work, a comprehensive vibrational behavior analysis is performed on anti-symmetric laminated composite plates resting on visco-elastic foundations undergoing thermal effects. Here, the governing equations of motion are developed through Hamilton's principle and Reddy's plate theory as higher-order shear deformation theory (HSDT) is employed...
Article
Full-text available
Morphing aircraft structures usually introduce greater compliance into aerodynamic sections, and therefore will affect the aeroelasticity with the potential risk of increased flutter. A low-fidelity model of an active camber morphing wing and its aeroelastic model are developed in order to investigate the potential critical speed by exploiting its...
Article
Robust design optimization (RDO) of large-scale engineering systems is computationally intensive and requires significant CPU time. Considerable computational effort is still required within conventional meta-model assisted RDO frameworks. The primary objective of this article is to minimize further the computational requirements of meta-model assi...
Article
This paper presents an extensive review of the developments in the aeroelasticity of morphing aircraft that occurred in the last decade (from 2009 to 2020). It focuses mainly on fixed-wing aircraft and highlights some representative examples from rotary-wing aircraft. Morphing wings are usually associated with significant changes in the aerodynamic...
Chapter
Bayesian methods have become very popular in the area of finite element model updating (FEMU) in the last decade, where these methods are considered as powerful tools in quantifying the uncertainties associated with the modelling and the experimental processes. Based on Bayes’ theorem, the posterior distribution function can be employed to describe...
Article
In this study, the aeroelastic instability of a wing with an initial out-of-plane curvature is determined. The structural dynamics of the wing is modelled by using the geometrically exact beam equations, and the aerodynamic loads are determined using an incompressible unsteady aerodynamic model. The wing is considered to have initial out-of-plane c...
Article
Full-text available
Recent theory has predicted the onset of asynchronous bouncing motion at speeds beyond those of internal resonance in multi-degree-of-freedom rotating systems with intermittent contact. This paper provides the first attempt to experimentally validate the theory. Vibrations incorporating rotor-stator contact are recorded from a vertically ounted rot...
Article
Full-text available
The steady-state response of a strongly nonlinear system often has multiple solutions under harmonic excitation, which includes both multiple response amplitudes and multiple phases. Taking advantage of the force dropout phenomenon of electrodynamic shakers near resonance, a fixed frequency test method was proposed previously to measure the multiva...
Article
In this paper, the dynamics of a tailored composite rotating blade with curved tips are investigated, with a view to improving the dynamic behaviour of the blade in flight. The blade tip is curved either in the out-of-plane or in the in-plane directions. The composite blade is modelled by using the exact beam formulation, and the cross-sectional pr...
Article
Full-text available
A passive energy balancing concept for linear actuation is investigated in the current work by adopting a negative stiffness mechanism. The proposed negative stiffness mechanism uses a pre-tensioned spring to produce a passive torque and therefore to transfer the passive torque through a crankshaft for linear motion. The proposed passive energy ba...
Article
A comprehensive vibrational analysis of bi-directional functionally graded (2D-FG) rotating nanobeams with porosities is studied for the first time. The beam is modeled based on general nonlocal theory (GNT) where the beam governing equations are derived depending on two different nonlocal parameters. Unlike Eringen’s conventional form of nonlocal...
Article
Full-text available
The purpose of this paper is to provide a high-order finite element method (FEM) formulation of nonlocal nonlinear nonlocal graded Timoshenko based on the weak form quadrature element method (WQEM). This formulation offers the advantages and flexibility of the FEM without its limiting low-order accuracy. The nanobeam theory accounts for the von Kár...
Article
For the first time, the structural dynamics and vibrational stability of a viscoelastic axially functionally graded (AFG) beam with both spinning and axial motions subjected to an axial load are analyzed, with the aim to enhance the performance of bi-gyroscopic systems. A detailed parametric study is also performed to emphasize the influence of var...
Conference Paper
Stochastic model updating of joints is a common solution for realistic modelling of built-up structures. However, detailed large-scale models render the simulations to be computationally expensive. This issue is addressed in the following two ways. The first approach involves stochastic decomposition of the functional space by machine learning tech...
Conference Paper
29th Biennial Conference on Noise and Vibration Engineering, ISMA2020
Article
Full-text available
The experimental characterisation of a nonlinear structure is a challenging process, particularly for multiple degree of freedom and continuous structures. Despite attracting much attention from academia, there is much work needed to create processes that can achieve characterisation in timescales suitable for industry, and a key to this is the des...
Chapter
A standard finite element analysis of individual components in aero engine and other systems shows a high accuracy compared to experimental measurements of the system response. However when it comes to assemblies, the conventional linear approaches fail to deliver good accuracy. This is due to the uncertain physical phenomena in the contact interfa...